1. Field of the Invention
The present invention relates to the field of mass spectrometry, and more particularly to the field of removable ionization chambers and removable components in associated ion guides that are often configured for mass spectrometers.
2. Discussion of the Related Art
The ion source utilized in conventional mass spectrometers can include an ion volume, a lens stack, and a radio frequency (RF) multipole ion guide. Currently, the ion volume can be removed without venting the instrument. Such an arrangement enables a user to remove the contaminated parts associated with the ion volume, clean them, or replace them so as to continue operating the instrument without breaking the vacuum. However, such a solution only works when the cleanliness of parts configured within the ion volume is the limiting factor in restoring the ion source performance. When the lens stack or the ion guide becomes contaminated such that the instrument sensitivity is inadequate, the instrument must be vented and the entire source must be removed for cleaning.
Background information for an system having interchangeable ionization chambers, is described and claimed in U.S. Pat. No. 4,388,531, entitled “Ionizer Having Interchangeable Ionization Chamber,” issued Jun. 14, 1983, to Stafford et al., including the following, “An ionizer adapted to be placed in a vacuum envelope for providing ions of a sample to be analyzed is disclosed herein and includes an electron source, ion accelerating and focusing electrodes and an interchangeable ionization chamber . . . . ”
Additional background information for a mass spectrometer having a replaceable ionization chamber, is described and claimed in U.S. Pat. No. 3,723,729, entitled “Ionization Chamber For Use With A Mass Spectrometer,” issued Mar. 27, 1973, to Kruger et al., including the following, “A replaceable ionization chamber for a mass spectrometer comprises an ionization region defined by two parallel perforated membranes attached to concentric tubular electrodes which are separated by the ionization region. Two filaments and two electron focusing electrodes are symmetrically disposed about the periphery of the ionization region, and sample input ports are similarly disposed about the periphery.”
Background information for a mass spectrometer having segmented RF ion guides, is described and claimed in U.S. Pat. No. 7,034,292 B1, entitled “Mass Spectrometry With Segmented RF Multiple Ion Guides In Various Pressure Regions,” issued Apr. 25, 2006, to Whitehouse et al., including the following, “A mass spectrometer is configured with individual multipole ion guides, configured in an assembly in alignment along a common centerline wherein at least a portion of at least one multipole ion guide mounted in the assembly resides in a vacuum region with higher background pressure, and the other portion resides in a vacuum region with lower background pressure. Said multipole ion guides are operated in mass to charge selection and ion fragmentation modes, in either a high or low pressure region, said region being selected according to the optimum pressure or pressure gradient for the function performed. The diameter, lengths and applied frequencies and phases on these contiguous ion guides may be the same or may differ. A variety of MS and MS/MSn analysis functions can be achieved using a series of contiguous multipole ion guides operating in either higher background vacuum pressures, or along pressure gradients in the region where the pressure drops from high to low pressure, or in low pressure regions. Individual sets of RF, +/−DC and resonant frequency waveform voltage supplies provide potentials to the rods of each multipole ion guide allowing the operation of ion transmission, ion trapping, mass to charge selection and ion fragmentation functions independently in each ion guide.”
Accordingly, a large customer need exists for a single mass spectrometer ion source sub-assembly (i.e., an ion source, lens stack, and a pre-filter configured as part of the ion guide), which collectively can be removed from the instrument without venting the system. Such an arrangement allows a user to clean all parts of the ion path that get contaminated in normal operation in a time efficient manner. The present invention is directed to such a need.